如何在C#中移除XML首行后的一个制表符以规范格式

问题场景 #

原始XML字符串：

<?xml version="1.0" encoding="utf-16"?>
    <reportResponse>
      <report>
        <inquiry>
          <agencyId>32</agencyId>
          <archiveId>4055062521111790</archiveId>
          <originalArchiveId>0</originalArchiveId>
          <sequenceNr>0</sequenceNr>
        </inquiry>
      </report>
    </reportResponse>

需要调整为层级规范的格式，移除首行后所有行开头的4个空格（对应一个制表符的缩进量）：

<?xml version="1.0" encoding="utf-16"?>
<reportResponse>
  <report>
    <inquiry>
      <agencyId>32</agencyId>
      <archiveId>4055062521111790</archiveId>
      <originalArchiveId>0</originalArchiveId>
      <sequenceNr>0</sequenceNr>
    </inquiry>
  </report>
</reportResponse>

实现方案 #

方案1：逐行处理字符串 #

直接拆分字符串为行，首行保留，后续行移除开头的指定缩进：

string originalXml = @"<?xml version=""1.0"" encoding=""utf-16""?>
    <reportResponse>
      <report>
        <inquiry>
          <agencyId>32</agencyId>
          <archiveId>4055062521111790</archiveId>
          <originalArchiveId>0</originalArchiveId>
          <sequenceNr>0</sequenceNr>
        </inquiry>
      </report>
    </reportResponse>";

// 按系统换行符拆分，保留所有行
string[] lines = originalXml.Split(new[] { Environment.NewLine }, StringSplitOptions.None);

// 从第二行开始，移除开头的4个空格
for (int i = 1; i < lines.Length; i++)
{
    if (lines[i].StartsWith("    "))
    {
        lines[i] = lines[i].Substring(4);
    }
}

string formattedXml = string.Join(Environment.NewLine, lines);

方案2：正则表达式批量替换 #

用正则匹配首行后的行开头缩进，一次性替换：

using System.Text.RegularExpressions;

string originalXml = @"<?xml version=""1.0"" encoding=""utf-16""?>
    <reportResponse>
      <report>
        <inquiry>
          <agencyId>32</agencyId>
          <archiveId>4055062521111790</archiveId>
          <originalArchiveId>0</originalArchiveId>
          <sequenceNr>0</sequenceNr>
        </inquiry>
      </report>
    </reportResponse>";

// 匹配首行之外的所有行开头的4个空格，替换为空
string formattedXml = Regex.Replace(originalXml, @"^(?<!\A)    ", "", RegexOptions.Multiline);

方案3：XML解析器重新格式化（推荐） #

如果XML结构复杂，用官方XML解析器处理更稳妥，能自动生成规范缩进：

using System.Xml;
using System.Text;

string originalXml = @"<?xml version=""1.0"" encoding=""utf-16""?>
    <reportResponse>
      <report>
        <inquiry>
          <agencyId>32</agencyId>
          <archiveId>4055062521111790</archiveId>
          <originalArchiveId>0</originalArchiveId>
          <sequenceNr>0</sequenceNr>
        </inquiry>
      </report>
    </reportResponse>";

XmlDocument doc = new XmlDocument();
doc.LoadXml(originalXml);

XmlWriterSettings settings = new XmlWriterSettings
{
    Indent = true,
    IndentChars = "  ", // 用两个空格作为缩进单位
    OmitXmlDeclaration = false,
    Encoding = Encoding.Unicode // 对应utf-16编码
};

using (StringWriter sw = new StringWriter())
using (XmlWriter writer = XmlWriter.Create(sw, settings))
{
    doc.WriteTo(writer);
    writer.Flush();
    string formattedXml = sw.ToString();
}

内容的提问来源于stack exchange，提问作者Sajeel